Ion mobility spectrometers are analytical instruments used to investigate properties of charged particles by separating the charged particles, i.e., ions, in time as a function of ion mobility. In the typical ion mobility spectrometers, an electric drift field is established in a drift tube filled with a buffer gas, and as the ions move through the drift tube under the influence of the electric drift field the ions collide with the buffer gas and separate as a function their collision cross-sections such that more compact conformers reach the end of the drift tube faster than less compact conformers. Known drift tubes may be so-called single-pass drift tubes, i.e., linear or non-linear drift tubes through which ions traverse only once between ion inlets and outlets thereof, or so-called multiple-pass drift tubes, i.e., linear or closed-path drift tubes through which ions may traverse multiple times before exit.